Housing for tool mechanism



May 13, 1969 w. BAKER ET AL 3,443,646

HOUSING FOR TOOL MECHANISM Filed March 16, 1967 JOSEPH F. CARTER W/LL/AM J. BAKER INVENTORS ATTORNEY United States Patent O 3,443,646 HOUSING FOR TOOL MECHANISM William J. Baker, Reed City, and Joseph F. Carter, Grand Haven, Mich., assignors to Gardner-Denver Company, a corporation of Delaware Filed Mar. 16, 1967, Ser. No. 623,582 Int. Cl. B23b 45/04; B27c 3/08 US. Cl. 173169 ABSTRACT OF THE DISCLOSURE A tool housing having a molded nonmetallic pistol-grip handle and a barrel with a metal sleeve pressed into the bore of the barrel for receiving a motor and motor-driven tool components.

BACKGROUND OF THE INVENTION Pistol-grip hand tools usually include a main member which comprises a metal casting having a cylindrically bored barrel for receiving and retaining the operating parts of the tool. The bore of the metallic barrel is dimensioned for a close fit with certain of the operating tool parts and provides a rigid mounting for bearings and the like which support the moving tool parts. Commonly the metal handle and barrel portions of the tool provide passages for motive fluid, such as compressed air, which is supplied to an air motor for driving the moving tool parts to produce useful work such as fastener driving, hole drilling, impacting, wire wrapping, and operations of a similar nature. The substitution of moldable, nonmetallic material for metal in the housing of such tools presents the following problems which, among others, this invention is intended to solve:

(1) The nonmetallic material defining the housing barrel tends to exhibit poorer dimensional stability than does metal and has less strength.

(2) The bore of the barrel may lack dimensional accuracy or smoothness in the as-molded condition whereby acceptable sealing fits between the barrel bore and parts mounted therein are unobtainable.

(3) Threads cut in the nonmetallic barrel openings for retaining structurally associated metal parts tend to break out under stress and to deteriorate after only a few disassembly and reassembly operations.

SUMMARY OF THE INVENTION The invention resides in a pistol-grip housing for a hand tool wherein the barrel portion and the handle portion are integrally molded of a deformable, nonmetallic material, such as plastic, and the bore of the barrel is fitted with a metal sleeve or liner. The metal sleeve is pressed longitudinally into the bore of the premolded barrel and the sleeve is exteriorly tapered with respect to the interior taper of the barrel bore so that a short longitudinal press of the sleeve will induce in the barrel a predetermined radial pressure along the length of the barrel. The metal sleeve receives the tool mechanism, and the sleeve may be provided with threaded closures at its opposite ends to retain the parts of the mechanism in proper assembly. The assembled sleeve and barrel have a pressure-induced, airtight fit along the length of their engagement with one another to prevent motive air supplied to the tool from leaking therebetween to atmosphere. These advantages, among others, are provided in the plastic tool housing and metal sleeve combination according to this invention:

(1) Compared to a metal housing of the same size and configuration, the plastic housing is lighter in weight thereby increasing the ease of manipulation of the tool and reducing operator fatigue where the tool is employed to 7 Claims perform highly repetitive operations. Operator comfort and efficiency are further enhanced by the more pleasingto-the-touch characteristic of plastic handle material.

(2) Since the plastic of the housing is an insulating material, the operator is protected from the hazard of electric shocks should the tool housing accidently contact an energized electrical conductor.

(3) A molded plastic tool housing comprises a relatively low-cost part compared to a metal casting intended for the same purpose.

(4) The predetermined stress induced in the plastic barrel serves to retain the metal sleeve in proper assembly with the barrel and, in many plastic materials, enhances the dimensional stability of the barrel wall.

(5) Radial stretching of the barrel wall due to the tapered press fit between the molded barrel and the sleeve causes plastic flow of projecting irregularities on the interior barrel surface into deformed, sealing engagement with the smooth exterior surface of the rigid sleeve.

Other objects and advantages of this invention will become apparent upon reading the following description and claims in connection with the attached drawing which is a longitudinal section.

The tool shown in the accompanying drawing comprises a main housing member, generally designated by numeral 10, a sleeve or liner 12 disposed within the housing 10, a rear closure cap 14 and a front nose piece 16 secured at opposite ends of the sleeve 12, and an operating mechanism disposed within sleeve 12 and indicated in its entirety by numeral 17.

In the illustrative embodiment of the invention, the housing 10 comprises an elongated barrel portion 18 and an integral handle portion 20 which depends at an angle to the barrel to provide a conventional pistol-grip tool housing. The barrel 18 has a longitudinal bore 22 extending therethrough and opening at the front end 24 and rear end 26 thereof. The handle 20 is shaped and sized to be comfortably gripped by the hand of an operator and is provided with generally parallel spaced passages 30 and 32 which communicate between the bottom handle surface 34 and the barrel bore 22. Passage 32 serves as the inlet for compressed air which is supplied to an air operated rotary motor component 36 of the tool mechanism 17. An air supply conduit, not shown, may be connected to the threaded fitting 38 disposed in the lower end of handle passage 32. A suitable air inlet valve 40 is operable in a well understood manner by a digitally depressible trigger mechanism 42 for controlling the admission of motive air to the motor 36. The upper end of the air inlet passage 32 is substantially aligned with an air inlet aperture 44 in the sleeve 12; and, motive air flows through the aperture 44 into an annular chamber 46 and then is communicated to the inlet of the motor 36 through aligned passages, not shown, in a spacer 47, a speed reduction gear assembly 48, and a motor front end plate 50. An air outlet aperture 52 in sleeve 12 which is longitudinally spaced from the inlet aperture 44 communicates between the air exhaust ports 54 of motor 36 and the upper end of the exhaust passage 30; and, the lower end of the exhaust passage 30 opens to atmosphere at the bottom surface 34 of handle 20.

The sleeve 12 is longitudinally coextensive with the barrel 26 and is internally threaded at its opposite ends to receive reduced threaded portions of the rear closure cap 14 and the front nose piece 16, respectively. The cap 14 closes the rear end of the bore of the sleeve 12 and has an enlarged head portion 56 which overlies the extreme rear end surface of the barrel 18. The reduced threaded portion 58 of the cap 14 terminates in an annular surface 60 which compressively engages a spring Washer 62. A retaining ring 64 is fixedly mounted in a mating groove relieved in the interior wall of the sleeve 12 adjacent the spacer 46. The spring washer 62 is pressed against the motor rear end plate 66 by the cap 14 thereby retaining the rear end plate 66, the motor 36, the front end plate 50, the gear mechanism 48 and the spacer 47 in their proper assembled relationship within the sleeve 12.

A rotary spindle 68 projects forwardly from the front end 24 of the barrel 18 and any desired work implement, such as that indicated by numeral 70, may be attached to the spindle. The spindle 66 is rotatively driven by the motor component 36 of the tool mechanism and is housed and journaled by a spindle housing 72 disposed in the front portion of the sleeve 12. The spindle housing is removably retained in the sleeve 12 by the front nose piece 16 which has a reduced threaded portion 74 which engages with internal threads at the front end of the sleeve 12. The spindle housing 72 is held between the retaining ring 64 and the rear surface 76 of the nose piece which bears against an annular shoulder 78 of the spindle housing. A reduced diameter portion 80 of the spindle housing extends through the stepped bore 82 of the nose piece 16 in spaced relation thereto. From the foregoing description it will be appreciated that the entire tool mechanism 17 can be removed from the sleeve for inspection or repair by unscrewing the end cap 14 and the nose piece 16.

An important feature of this invention is the provision of a tool mechanism housing, such as housing 10, which is molded of nonmetallic material, and which, in comparison to a cast metal housing, is inexpensive, lightweight, electrically nonconductive and pleasing to the touch. A wide choice of materials meeting these require ments is available in the general field of polymers; and, while the present invention is not limited to any particular type of polymer, the selected housing material should have good impact strength, dimensional stability, creep resistance and low mold shrinkage. A preferred type of engineering quality thermoplastic which meets these performance requirements and is commercially available is polycarbonate resin. There remain, however, certain problems in the use of even the most desirable plastic materials in housings for the operating mechanisms of tools such as drills, screwdrivers, nutsetters, impact wrenches, wire wrappers, tappers, and the like, since even changes of a low order in the dimension or shape of the housing due to dimensional instability or creepage of the material may cause the interacting parts of the mechanism to bind or otherwise malfunction. The present invention effectively overcomes this problem by the provision of a rigid member, such as the metal sleeve 12, for receiving and retaining the tool mechanism inside the nonmetallic, plastic housing barrel 18. The sleeve 12 is sufiiciently rigid to maintain such parts as the motor 36, the reducing gears 48 and the spindle 66 in proper driving alignment. Moreover, the sleeve has sufiicient strength to resist denting or bending should the tool be dropped or otherwise impacted. The aforementioned threads for attaching the closure cap 14 and the nose piece 16 are formed on the metal sleeve 12 and are stronger and, therefore, more durable than would be the case if these threads were cut in the ends of the nonmetallic barrel 18.

The provision of the metal sleeve 12 in the barrel 18 not only makes a plastic tool housing practical, but, in accordance with this invention, the sleeve and barrel coact to produce other unexpected advantages.

The bore 22 of the barrel 18 is tapered from the rear end 26 to the front end 24 of the barrel; and, the exterior surface of the sleeve 12 is also tapered from its rear end to its front end. The tapers of the bore 22 and the sleeve 12 are selected to provide a pressure fit between these parts by pressing the sleeve into the bore in the forward direction, i.e., toward the front end 24 of the barrel, until the end surfaces of the sleeve 12 and the barrel 18 register with one another. In a preferred embodiment of the housing, a sleeve taper of .0121 inch per inch is employed and the bore taper is such that the length of press required to assemble the sleeve is approximately .3125 inch. The taper rates of the sleeve 12 and the bore 22 and the length of press should be selected so that the wall of the barrel 18 will be stressed to a predetermined degree such that a tight pressure fit exists between the barrel 18 and the sleeve 12 along the entire length thereof. Depending upon the physical properties of the selected housing material, the barrel wall will be elastically or plastically deformed during the pressing operation and can be said to be stretched about the relatively nondeformable sleeve. The stress level in the barrel wall induced by the press fit of the sleeve therein should not, however, be so great as to cause the barrel wall to rupture.

The stress-induced radial pressure between the sleeve 12 and barrel 18 serves not only to retain these parts in assembled relation, but is also intended to provide an airtight seal therebetween. In the illustrative tool such a seal prevents motive air from leaking between the barrel and sleeve to atmosphere at the ends of the barrel; and, the sealing engagement between these parts in the area between the apertures 44 and 52 prevents direct communication between the air inlet and exhaust passage 32 and 30. Without such sealing engagement, special means, such as O-rings would be required to perform the above mentioned sealing function. Even if the surface of the barrel bore 22 is somewhat irregular in its as-molded condition, it is anticipated that, during the assembly of the sleeve 12 into the bore 22, the pressure acting on the internal barrel wall will cause the wall material to fiow into sealing engagement with the relatively smooth exterior surface of the sleeve 12. If the selected housing material is not readily flowable during assembly of the sleeve or if the molding method employed produces an extremely rough surface in the bore 22, a thin coating of epoxy resin, or other material of a similar nature, can be applied to the sleeve 12 and the bore 22 prior to assembly. The epoxy will fill any voids between the sleeve and the bore and, due to the adhesive quality of the epoxy, it will serve to join the sleeve and the barrel together.

The stress set up in the wall of the barrel as an incident to pressing the sleeve into the barrel can have a good effect on certain physical properties of many thermoplastic materials which are suitable for carrying out this invention. For example, by properly establishing the stress in the barrel wall at a determinable optimum level, creep in the wall material becomes minimum and can be neglected in long-term, continuous-load applications such as this invention contemplates. This unexpected result from the pressure fit of the sleeve 12 in the barrel 18 provides improved dimensional stability of the barrel and may also improve the barrels resistance to denting due to random impacting in the course of use of the tool.

From the foregoing description, it will be appreciated that the principal feature of this invention is the provision of a tool mechanism housing made of plastic or other suitable nonmetallic material which structurally incorporates a rigid metallic sleeve within which the mechanism can be satisfactorily mounted. By this means the several above enumerated advantages derivable from the substitution of plastic for metal in the housing member are obtainable. Another feature of this invention is the provision of a taper-induced pressure fit between the housing barrel 18 and metal sleeve 12 in order to retain the sleeve in the barrel without special locking means, in order to produce and maintain an airtight seal between the sleeve and the barrel, and in order to enhance the physical properties of the barrel.

While the illustrated embodiment of the invention comprises a housing for an air-operated rotary tool, most or all of the advantageous features of the invention could be incorporated in reciprocating tools having air-actuated pistons, or the like, and also in electric motor driven tools of many types. It will also be apparent to those skilled in this art that various changes in construction, proportion, arrangement and materials of the described tool mechanism housing may be made without sacrificing any of the advantages of the invention or departing from the scope of the appended claims.

Having fully disclosed the invention, we claim: 1. A housing for fiuid actuated motor, comprising: a nonmetallic barrel having a deformable Wall defining a longitudinal bore; a rigid sleeve for receiving said motor; said barrel and said sleeve coacting to define fiuid passage means for said motor; and said sleeve being fitted into said bore and deforming said wall to provide a fluid-tight seal therebetween to prevent passage of fluid between said barrel and said sleeve. 2. The housing defined in claim 1, wherein said bore and said sleeve are tapered to provide a pressure fit therebetween. 3. The housing defined in claim 2, wherein said bore and said sleeve open to both ends of said barrel; and said bore and said sleeve are longitudinally coextensive. 4. The invention defined in claim 3, wherein at least one open end of said sleeve is threaded to coact with a matingly threaded member to close said at least one end. 5. The invention defined in claim 1 wherein a manually grippable handle is integrally formed with said 6. The invention defined in claim 5, wherein said passages open to said bore in substantial alignment with said apertures; and

said sleeve and said wall coact to provide a seal therebetween to prevent direct communication between said apertures.

7. A housing for the operating mechanism of a tool,

comprising:

a nonmetallic barrel having a deformable wall defining a longitudinal bore;

a rigid sleeve fitted into said bore and deforming said wall to provide a pressure fit between said sleeve and said wall;

said mechanism being disposed in said sleeve; and

a thin layer of adhesive material disposed in said bore between said wall and said sleeve for fitting voids therebetween.

References Cited UNITED STATES PATENTS 1,362,657 12/1920 Whyte 173-171 X 2,048,096 7/ 1936 Bisley 173-171 X 2,342,319 2/ 1944 Youhouse 173-171 X 2,655,963 10/1953 Dell 173-169 X 3,043,274 7/1962 Quackenbush 173-169 X 3,119,942 1/ 1964 Luther 173-171 3,159,025 12/1964 Pais 173-170 X OTHER REFERENCES Marks Mechanical Engineers Handbook sixth edition,

McGraw-Hill Book Co., Baumeister. Pages 8-56 through 8-60 relied on.

NILE C. BYERS, JR., Primary Examiner.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,646 Dated May 13, 1969 Inventor(s) William J. Baker and Joseph F. Carter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I Claim 7, column 6, line 16 change "fitting to filling SIGNED AND SEALED 001'28t969 (SEAL) Attest:

Edward M. Fletcher, wmmm E. 50mm, m. Arresting Officer Gomissioner of Patents 

